General Pathology — MCQs

A child is born with a single functional copy of a tumor suppressor gene. At the age of 5 years, the remaining normal allele is lost through mutation, resulting in the loss of control over the transition from G1 to the S phase of the cell cycle. Which of the following neoplasms is most likely to arise by this mechanism?

Q640Easy

A patient who previously had good muscle mass now presents with decreased muscle mass. There is a history of road traffic accident that led him to be bedridden for 6 months. This decrease in muscle mass is best explained by which of the following cellular adaptations?

General Pathology Indian Medical PG Practice Questions and MCQs

Question 631: Which of the following chromosomal abnormalities is NOT typically associated with Down syndrome?

A. Translocation t(14:21)
B. Trisomy 21
C. Translocation t(11:14) (Correct Answer)
D. Translocation t(15:21)

Explanation: **Explanation:** Down syndrome (Trisomy 21) is the most common chromosomal disorder [1]. It results from an extra copy of genetic material on chromosome 21, which can occur through three distinct cytogenetic mechanisms [1]. **Why Option C is Correct:** **Translocation t(11:14)** involves the fusion of the *CCND1* gene (cyclin D1) on chromosome 11 with the *IGH* (immunoglobulin heavy chain) locus on chromosome 14. This abnormality is the hallmark of **Mantle Cell Lymphoma**, a B-cell malignancy. It has no association with Down syndrome, as it does not involve chromosome 21. **Why the Other Options are Incorrect:** * **Option B (Trisomy 21):** This is the most common cause (95% of cases), typically due to **meiotic non-disjunction** (most often during maternal meiosis I) [3]. * **Options A & D (Robertsonian Translocations):** Approximately 4% of cases are caused by the attachment of the long arm of chromosome 21 to another acrocentric chromosome (usually 14 or 15) [1]. Unlike non-disjunction, these cases can be inherited from a carrier parent, increasing the recurrence risk in future pregnancies [2]. **NEET-PG High-Yield Pearls:** * **Most common cause:** Meiotic non-disjunction (correlated with advanced maternal age) [3]. * **Mosaicism (1%):** Results from mitotic non-disjunction during early embryogenesis; these patients often have a milder phenotype [2]. * **Screening:** First trimester (Low PAPP-A, High β-hCG, increased Nuchal Translucency) and Quadruple screen (Low AFP, Low Estriol, High hCG, High Inhibin A). * **Associated Conditions:** Early-onset Alzheimer’s (APP gene on Ch 21), Acute Leukemia (AMKL/M7 and ALL), and Duodenal atresia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 171-172. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 170-171. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 92-93.

Question 632: Which of the following is an autosomal recessive disease?

A. Tuberous sclerosis
B. Duchenne muscular dystrophy
C. Cystic fibrosis (Correct Answer)
D. All

Explanation: **Explanation:** The correct answer is **Cystic Fibrosis**. This condition is a classic example of an **Autosomal Recessive (AR)** disorder [1], caused by a mutation in the *CFTR* gene on chromosome 7. In AR inheritance, an individual must inherit two copies of the mutated gene (one from each parent) to manifest the disease. **Analysis of Options:** * **Cystic Fibrosis (Correct):** It is the most common lethal genetic disease in Caucasian populations [2]. The defect in chloride channel function leads to thick, viscid secretions affecting the lungs, pancreas, and reproductive system. * **Tuberous Sclerosis (Incorrect):** This is an **Autosomal Dominant (AD)** neurocutaneous syndrome. It is characterized by the triad of seizures, mental retardation, and angiofibromas (Vogt’s triad). It involves mutations in *TSC1* (Hamartin) or *TSC2* (Tuberin) genes. * **Duchenne Muscular Dystrophy (Incorrect):** This is an **X-linked Recessive (XLR)** disorder. It is caused by a mutation in the *Dystrophin* gene (the largest known human gene), leading to progressive muscle degeneration. **NEET-PG High-Yield Pearls:** 1. **Mnemonic for AR Disorders:** "ABCDE-S"—**A**lkaptonuria, **B**enign Prostatic Hyperplasia (not genetic, but used for flow), **C**ystic Fibrosis/Congenital Adrenal Hyperplasia, **D**eafness (sensorineural), **E**nzyme deficiencies (most inborn errors of metabolism), and **S**ickle cell anemia/Thalassemia [1]. 2. **Rule of Thumb:** Most structural protein defects are Autosomal Dominant, while most enzyme deficiencies are Autosomal Recessive [3]. 3. **Cystic Fibrosis Diagnosis:** The gold standard is the **Sweat Chloride Test** (pilocarpine iontophoresis) showing chloride levels >60 mmol/L. 4. **Common Mutation:** The most frequent mutation in Cystic Fibrosis is **ΔF508** (deletion of phenylalanine at position 508). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 150-151. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 120-122. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 57-58.

Question 633: Which of the following is a tumor marker?

A. Acid hydrolase
B. Alkaline phosphatase (Correct Answer)
C. Melatonin
D. CPK-MB

Explanation: **Explanation:** **Alkaline Phosphatase (ALP)** is the correct answer because it serves as a biochemical tumor marker in specific clinical contexts. While ALP is found in various tissues (liver, bone, placenta), certain isoenzymes are associated with malignancies. Specifically, the **Regan isoenzyme** (a placental-like ALP) is a classic tumor marker for **seminoma** and certain gynecological cancers. Additionally, elevated serum ALP is a high-yield indicator of osteoblastic activity in **bone metastasis** (e.g., from prostate cancer) [1] and space-occupying lesions in the liver (e.g., **Hepatocellular Carcinoma**). **Analysis of Incorrect Options:** * **Acid Hydrolase:** These are lysosomal enzymes (e.g., acid phosphatase) involved in intracellular digestion. While Prostatic Acid Phosphatase (PAP) was historically used for prostate cancer, "acid hydrolase" is a general functional category, not a specific tumor marker. * **Melatonin:** This is a hormone secreted by the pineal gland that regulates sleep-wake cycles. It has no clinical utility as a diagnostic tumor marker. * **CPK-MB:** This is a cardiac biomarker used specifically for diagnosing **Acute Myocardial Infarction (AMI)**. It indicates myocardial muscle damage, not neoplastic growth. **High-Yield Clinical Pearls for NEET-PG:** * **Regan Isoenzyme:** Heat-stable ALP; mimics placental ALP; associated with Seminoma. * **Nagao Isoenzyme:** Associated with germ cell tumors and metastatic carcinoma. * **Other Enzyme Markers:** Remember **LDH** (Dysgerminoma/Lymphoma) and **PSA** (Prostate Cancer) as frequently tested enzymatic tumor markers [2]. * **ALP Elevation:** Always differentiate between hepatic (obstructive jaundice) and skeletal (Paget’s disease, bone mets) causes using GGT levels. [Note: Tumors may inappropriately synthesize substances not normally expressed due to gene derepression, facilitating their use as markers [3].] **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 501-502. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 254-255. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 213-214.

Question 634: A 35-year-old woman presents with a firm, painless, round lump in her right breast following a traumatic injury. Which statement is false regarding the condition she is experiencing?

A. Dystrophic calcification can be seen
B. Liquefactive fat necrosis may occur
C. Multinucleate giant cells and lipid-laden macrophages are present
D. There is an increased risk of breast cancer (Correct Answer)

Explanation: **Explanation:** The clinical presentation of a firm, painless lump following trauma in the breast is characteristic of **Fat Necrosis**. **1. Why Option D is the Correct (False) Statement:** Fat necrosis is a **benign, inflammatory process** resulting from the release of fatty acids from injured adipocytes. It is strictly a reactive condition and **does not increase the risk of breast cancer**. Its clinical significance lies in its ability to mimic carcinoma on physical examination (firm, fixed mass) and mammography (calcifications). **2. Analysis of Other Options:** * **Option A (Dystrophic calcification):** As the necrotic tissue heals, fatty acids bind with calcium (saponification), leading to dystrophic calcification. This is a classic feature seen on mammography as "eggshell" calcifications. * **Option B (Liquefactive fat necrosis):** While "liquefactive" is usually associated with CNS infarcts or abscesses, in the breast, the enzymatic breakdown of fat by lipases initially creates a liquefied area of fatty debris before it progresses to fibrosis. * **Option C (Giant cells and macrophages):** Histologically, fat necrosis is characterized by an inflammatory infiltrate. Macrophages ingest the released lipids (becoming **foamy/lipid-laden macrophages**), and a foreign-body giant cell reaction occurs around the necrotic debris. **Clinical Pearls for NEET-PG:** * **Key Histology:** Anucleated adipocytes (ghost cells), foamy macrophages, and multinucleated giant cells. * **Radiology:** May show a "radiolucent oil cyst" or eggshell calcifications. * **Differential:** Always differentiate from **Comedocarcinoma**, which shows *dystrophic* calcification but is malignant. * **Trauma History:** Only present in about 50% of fat necrosis cases; its absence does not rule out the diagnosis.

Question 635: Caspases are associated with which of the following processes?

A. Organogenesis (Correct Answer)
B. Hydropic degeneration
C. Collagen hyalinization
D. None of the above

Explanation: **Explanation:** **Caspases** (Cysteine-aspartic proteases) are the executioners of **Apoptosis** (programmed cell death) [1]. While often associated with pathological states, apoptosis is a fundamental physiological process required for normal development [2]. **1. Why Organogenesis is Correct:** During embryonic development (**Organogenesis**), apoptosis is essential for sculpting tissues and organs [4]. Caspases mediate the removal of redundant cells to create functional structures. Classic examples include: * **Interdigital space formation:** Removal of webs between fingers and toes [4]. * **Neural tube development:** Elimination of excess neurons. * **Lumen formation:** Hollow out structures like the bowel or heart chambers. Without caspase-mediated apoptosis, developmental anomalies like syndactyly (fused digits) would occur [4]. **2. Why the other options are incorrect:** * **Hydropic degeneration:** This is a form of **reversible cell injury** characterized by cellular swelling due to ATP depletion and failure of Na+/K+ pumps. It is not mediated by caspases. * **Collagen hyalinization:** This refers to a descriptive histological term where tissues appear glassy and pink (e.g., in old scars or vascular walls in hypertension). It is an extracellular protein deposition process, unrelated to the intracellular caspase cascade. **High-Yield Clinical Pearls for NEET-PG:** * **Initiator Caspases:** Caspase 8 & 9 (Intrinsic/Extrinsic pathways) [1]. * **Executioner Caspases:** Caspase 3, 6, and 7 (Caspase 3 is the most common). * **Inflammatory Caspase:** Caspase 1 (associated with Pyroptosis and the Inflammasome). * **Marker for Apoptosis:** Annexin V (binds to phosphatidylserine on the outer membrane) [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-65. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 63-64. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 67-69. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 81-82.

Question 636: Which of the following is true about apoptosis?

A. Migration of leukocytes
B. End products are phagocytosed by macrophages
C. Intranuclear fragmentation of DNA
D. All of the above (Correct Answer)

Explanation: Apoptosis, or "programmed cell death," is a highly regulated pathway of cell death where cells activate enzymes that degrade their own nuclear DNA and cytoplasmic proteins [1]. **Analysis of Options:** * **Intranuclear fragmentation of DNA (Option C):** This is a hallmark feature of apoptosis. Endonucleases cleave DNA into fragments of 180–200 base pairs, appearing as a characteristic **"DNA ladder"** on gel electrophoresis. * **End products are phagocytosed by macrophages (Option B):** Apoptotic cells break into membrane-bound **apoptotic bodies**. These express "eat-me" signals (like **Phosphatidylserine** on the outer membrane), leading to rapid phagocytosis by macrophages without releasing inflammatory cellular contents [2]. * **Migration of leukocytes (Option A):** While apoptosis is typically "non-inflammatory," the process of clearing apoptotic bodies involves the recruitment and migration of phagocytic leukocytes (macrophages) to the site [2]. Since all these processes occur during the stages of apoptosis, **Option D (All of the above)** is the correct choice. **High-Yield NEET-PG Pearls:** * **Morphology:** Cell shrinkage, chromatin condensation (most characteristic), and formation of cytoplasmic blebs/apoptotic bodies. * **Caspases:** These are the executioner enzymes (Cysteine proteases). **Caspase 9** is the initiator for the Intrinsic (Mitochondrial) pathway; **Caspase 8/10** for the Extrinsic (Death Receptor) pathway; and **Caspase 3** is the common executioner [1,3]. * **Bcl-2 Family:** Pro-apoptotic (Bax, Bak) vs. Anti-apoptotic (Bcl-2, Bcl-xL) [4]. * **Distinction:** Unlike necrosis, apoptosis involves **no inflammation** and the **plasma membrane remains intact** until phagocytosis [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-65. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 67-69. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 67. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 80-81.

Question 637: A cyst arising from an unerupted tooth is classified as which of the following?

A. Dentigerous cyst (Correct Answer)
B. Odontogenic keratocyst
C. Radicular cyst
D. Gorlin cyst

Explanation: **Explanation:** A **Dentigerous cyst** (also known as a follicular cyst) is the most common type of developmental odontogenic cyst [1]. It originates from the **reduced enamel epithelium** of the dental follicle and characteristically surrounds the crown of an **unerupted or impacted tooth**. Radiographically, it appears as a well-defined unilocular radiolucency attached to the cemento-enamel junction (CEJ). The most common site is the mandibular third molar. **Analysis of Incorrect Options:** * **Odontogenic Keratocyst (OKC):** Arises from the dental lamina. While it can be associated with unerupted teeth, it is defined by its unique histology (parakeratinized lining) and aggressive behavior rather than its association with an unerupted crown. * **Radicular Cyst:** This is an inflammatory cyst, not developmental. It arises from the **rests of Malassez** and is typically found at the apex of a **non-vital (carious) tooth** [1]. * **Gorlin Cyst (Calcifying Odontogenic Cyst):** A rare developmental lesion characterized by "ghost cells" and calcifications. While it can be associated with unerupted teeth, it is not the primary classification for a cyst arising specifically from the follicle of an unerupted tooth. **High-Yield Pearls for NEET-PG:** * **Most common developmental odontogenic cyst:** Dentigerous cyst [1]. * **Most common inflammatory odontogenic cyst:** Radicular cyst. * **Key Histology:** Dentigerous cysts are lined by thin, non-keratinized stratified squamous epithelium. * **Complications:** If left untreated, a dentigerous cyst can transform into an Ameloblastoma or Squamous Cell Carcinoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 741-742.

Question 638: Shell teeth are more common in which type of dentinogenesis imperfecta, according to Shield's classification?

A. Type 1
B. Type 2
C. Type 3 (Correct Answer)
D. Type 4

Explanation: **Explanation:** **Dentinogenesis Imperfecta (DI)** is a genetic disorder of tooth development characterized by translucent, discolored teeth and weakened dentin. According to the **Shield’s Classification**, Type 3 is the specific variant associated with "shell teeth." * **Why Type 3 is Correct:** **Shield’s Type III (Brandywine type)** is a rare isolate found in the Brandywine population of Maryland. It is clinically unique because it features **"shell teeth,"** where the enamel appears normal but the dentin is extremely thin. This results in dramatically enlarged pulp chambers that occupy almost the entire tooth, giving it a hollow, shell-like appearance on radiographs. * **Why the others are Incorrect:** * **Type 1:** This occurs in association with **Osteogenesis Imperfecta (OI)**. While teeth are translucent, they typically show premature pulp obliteration rather than shell-like enlargement. [1], [2] * **Type 2:** This is the most common type and is **not** associated with OI. It is characterized by bulbous crowns, cervical constriction, and early obliteration of pulp chambers. * **Type 4:** This is not a standard category in the classic Shield’s Classification (which consists of Types I, II, and III). **High-Yield Clinical Pearls for NEET-PG:** * **Genetic Mutation:** DI Type II and III are caused by mutations in the **DSPP gene** (Dentin Sialophosphoprotein). * **Radiographic Hallmark:** Look for "bulbous crowns" and "constricted necks" (thistle-tube appearance) in Type II, versus "enlarged pulp/thin dentin" in Type III. * **Differential Diagnosis:** Dentin Dysplasia (Type I and II) also affects dentin but presents with "rootless teeth" or "crescent-shaped" pulp chambers. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1186. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1186-1188.

Question 639: A child is born with a single functional copy of a tumor suppressor gene. At the age of 5 years, the remaining normal allele is lost through mutation, resulting in the loss of control over the transition from G1 to the S phase of the cell cycle. Which of the following neoplasms is most likely to arise by this mechanism?

A. Retinoblastoma (Correct Answer)
B. Breast carcinoma
C. Adenocarcinoma of colon
D. Cerebral astrocytoma

Explanation: **Explanation:** The clinical scenario describes **Knudson’s "Two-Hit" Hypothesis**, which is the hallmark of hereditary **Retinoblastoma** [1]. 1. **Why Retinoblastoma is correct:** The question specifies a germline mutation (born with one functional copy) followed by a somatic mutation (loss of the second allele) in a gene controlling the **G1 to S phase transition** [1]. This gene is the **RB1 gene**, which encodes the pRB protein [2]. In its hyperphosphorylated (inactive) state, pRB allows entry into the S phase, while in its hypophosphorylated state, it binds to the **E2F transcription factor**, preventing entry [3]. Loss of both alleles (the "two hits") leads to uncontrolled cell proliferation [1]. While sporadic cases occur, the hereditary form typically presents in early childhood (often before age 5) and is frequently bilateral [2]. 2. **Why other options are incorrect:** * **Breast carcinoma:** Most commonly associated with *BRCA1/BRCA2* (DNA repair) or *HER2/neu* (growth factor receptor) mutations [1]. While *TP53* can be involved (Li-Fraumeni), it is not the classic "two-hit" model for G1-S transition in a 5-year-old [2]. * **Adenocarcinoma of colon:** Primarily follows the **APC/β-catenin pathway** (FAP) or the **DNA Mismatch Repair pathway** (Lynch Syndrome). These typically manifest in later childhood or adulthood. * **Cerebral astrocytoma:** Associated with various mutations (e.g., *IDH1*, *TP53*, *EGFR*), but does not classically present via the specific RB-mediated G1-S mechanism described. **High-Yield Clinical Pearls for NEET-PG:** * **RB Gene Location:** Chromosome **13q14** [1]. * **The "Governor" of the Cell Cycle:** pRB is known as the governor because it regulates the G1-S checkpoint [3]. * **Associated Tumors:** Patients with hereditary retinoblastoma have a significantly increased risk of developing **Osteosarcoma** later in life. * **Microscopic Hallmark:** **Flexner-Wintersteiner rosettes** are characteristic of retinoblastoma [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 298-300. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 737-738. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 300-301.

Question 640: A patient who previously had good muscle mass now presents with decreased muscle mass. There is a history of road traffic accident that led him to be bedridden for 6 months. This decrease in muscle mass is best explained by which of the following cellular adaptations?

A. Metaplasia
B. Dysplasia
C. Hypertrophy
D. Atrophy (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Atrophy** **Why it is correct:** The clinical scenario describes a classic case of **Disuse Atrophy**. Atrophy is defined as a reduction in the size of an organ or tissue due to a decrease in cell size and number [1]. When a patient is bedridden for a prolonged period (6 months), the lack of mechanical load and reduced metabolic demands lead to a decrease in muscle fiber diameter [1]. At the molecular level, this occurs via two primary mechanisms: 1. **Decreased protein synthesis** due to reduced metabolic activity. 2. **Increased protein degradation** via the **Ubiquitin-Proteasome pathway**. 3. Additionally, nutrient deficiency or reduced stimulation can trigger **autophagy**, where cells "eat" their own organelles to survive. **Why the other options are incorrect:** * **A. Metaplasia:** This is a reversible change where one adult cell type is replaced by another (e.g., Columnar to Squamous in a smoker's airway). It does not involve a decrease in mass. * **B. Dysplasia:** This refers to disordered growth and maturation of epithelium (pre-cancerous change). It is characterized by loss of architectural uniformity and pleomorphism. * **C. Hypertrophy:** This is an increase in the size of cells resulting in an increase in the size of the organ (e.g., a bodybuilder’s muscles or a hypertensive heart) [3]. It is the opposite of what is described here. **NEET-PG High-Yield Pearls:** * **Mechanism of Atrophy:** The hallmark is the presence of **autophagic vacuoles** and the activation of **ubiquitin ligases**. * **Brown Atrophy:** In chronic wasting diseases, the accumulation of **Lipofuscin** (wear-and-tear pigment) in atrophied organs (like the heart) gives them a brownish discoloration [2]. * **Common Causes of Atrophy:** Denervation (polio), loss of endocrine stimulation (menopause), ischemia (senile atrophy of the brain), and pressure (tumor compressing adjacent tissue) [1], [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 90-91. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 47-49. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 46-47.

Practice by Chapter

Cell Injury and Cell Death

Practice Questions

Adaptations of Cellular Growth

Practice Questions

Accumulations and Deposits

Practice Questions

Acute and Chronic Inflammation

Practice Questions

Tissue Repair and Wound Healing

Practice Questions

Hemodynamic Disorders

Practice Questions

Genetic Disorders

Practice Questions

Environmental Pathology

Practice Questions

Nutritional Diseases

Practice Questions

Molecular Basis of Disease

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free